1,248 research outputs found
Information-rich Task Allocation and Motion Planning for Heterogeneous Sensor Platforms
This paper introduces a novel stratified planning algorithm for teams of heterogeneous mobile sensors that maximizes information collection while minimizing resource costs. The main contribution of this work is the scalable unification of effective algorithms for de- centralized informative motion planning and decentralized high-level task allocation. We present the Information-rich Rapidly-exploring Random Tree (IRRT) algorithm, which is amenable to very general and realistic mobile sensor constraint characterizations, as well as review the Consensus-Based Bundle Algorithm (CBBA), offering several enhancements to the existing algorithms to embed information collection at each phase of the planning process. The proposed framework is validated with simulation results for networks of mobile sensors performing multi-target localization missions.United States. Air Force. Office of Scientific Research (Grant FA9550-08-1-0086)United States. Air Force. Office of Scientific Research. Multidisciplinary University Research Initiative (FA9550-08-1-0356
Evolution on a smooth landscape
We study in detail a recently proposed simple discrete model for evolution on
smooth landscapes. An asymptotic solution of this model for long times is
constructed. We find that the dynamics of the population are governed by
correlation functions that although being formally down by powers of (the
population size) nonetheless control the evolution process after a very short
transient. The long-time behavior can be found analytically since only one of
these higher-order correlators (the two-point function) is relevant. We compare
and contrast the exact findings derived herein with a previously proposed
phenomenological treatment employing mean field theory supplemented with a
cutoff at small population density. Finally, we relate our results to the
recently studied case of mutation on a totally flat landscape.Comment: Revtex, 15 pages, + 4 embedded PS figure
Spitzer Space Telescope observatory planning and scheduling team
Launched as the space infrared telescope facility (SIRTF) in August, 2003 and renamed in early 2004, the Spitzer space telescope is performing an extended series of science observations at wavelengths ranging from 3 to 180 microns. The California Institute of Technology is the home of the Spitzer Science Center (SSC) and operates the science operations system (SOS), which supports science operations of the observatory. A key function supported by the SOS is the long-range planning and short-term scheduling of the observatory. This paper describes the role and function of the SSC observatory planning and scheduling team (OPST), its operational interfaces, processes, and tools
SRTR Program-Specific Reports on Outcomes: A Guide for the New Reader
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72405/1/j.1600-6143.2008.02178.x.pd
White Light Demonstration of One Hundred Parts per Billion Irradiance Suppression in Air by New Starshade Occulters
A new mission concept for the direct imaging of exo-solar planets called the New Worlds Observer (NWO) has been proposed. The concept involves flying a meter-class space telescope in formation with a newly-conceived, specially-shaped, deployable star-occulting shade several meters across at a separation of some tens of thousands of kilometers. The telescope would make its observations from behind the starshade in a volume of high suppression of incident irradiance from the star around which planets orbit. The required level of irradiance suppression created by the starshade for an efficacious mission is of order 0.1 to 10 parts per billion in broadband light. This paper discusses the experimental setup developed to accurately measure the suppression ratio of irradiance produced at the null position behind candidate starshade forms to these levels. It also presents results of broadband measurements which demonstrated suppression levels of just under 100 parts per billion in air using the Sun as a light source. Analytical modeling of spatial irradiance distributions surrounding the null are presented and compared with photographs of irradiance captured in situ behind candidate starshades
Wall-Crossing from Boltzmann Black Hole Halos
A key question in the study of N=2 supersymmetric string or field theories is
to understand the decay of BPS bound states across walls of marginal stability
in the space of parameters or vacua. By representing the potentially unstable
bound states as multi-centered black hole solutions in N=2 supergravity, we
provide two fully general and explicit formulae for the change in the (refined)
index across the wall. The first, "Higgs branch" formula relies on Reineke's
results for invariants of quivers without oriented loops, specialized to the
Abelian case. The second, "Coulomb branch" formula results from evaluating the
symplectic volume of the classical phase space of multi-centered solutions by
localization. We provide extensive evidence that these new formulae agree with
each other and with the mathematical results of Kontsevich and Soibelman (KS)
and Joyce and Song (JS). The main physical insight behind our results is that
the Bose-Fermi statistics of individual black holes participating in the bound
state can be traded for Maxwell-Boltzmann statistics, provided the (integer)
index \Omega(\gamma) of the internal degrees of freedom carried by each black
hole is replaced by an effective (rational) index \bar\Omega(\gamma)=
\sum_{m|\gamma} \Omega(\gamma/m)/m^2. A similar map also exists for the refined
index. This observation provides a physical rationale for the appearance of the
rational Donaldson-Thomas invariant \bar\Omega(\gamma) in the works of KS and
JS. The simplicity of the wall crossing formula for rational invariants allows
us to generalize the "semi-primitive wall-crossing formula" to arbitrary decays
of the type \gamma\to M\gamma_1+N\gamma_2 with M=2,3.Comment: 71 pages, 1 figure; v3: changed normalisation of symplectic form
3.22, corrected 3.35, other cosmetic change
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